[Shmason]

Tony,

Thanks for the detailed response. I appreciate it is frustrating when you are not with the equipment and dealing with a novice who doesn’t really understand circuit diagrams.

Tonight’s revelation is that the ring conv relay will operate the buzzer when pressed manually. I also disconnected the two wires leading to its coil and applied an independent power source; the relay activated and buzzer sounded. So I think it is fairly safe to say finding out why the ring conv relay doesn’t activate is key to all this. I have copied your earlier message below and will comment in capitals to save time with formatting. I’M NOT SHOUTING!!!

Now we have Exch-to-Extn operated, so contact KE5 is open, disconnecting the 'main unit' bell. KE1 is changed over, so the B wire (terminal 4 in the main unit) goes out on terminal 1 to the relay coil in the ringing converter. Contact A2 (part of the relay inside the plinth) should be open as relay A is not energised, so the relay coil is not shorted out. The other side of the relay coil comes back on terminal 9, then via KA1 or KB1 (both not operated) to the bells in the extensions, then to earth (and thus back to the A wire which is assumed to be earthed at the exchange)

WHEN EXCH TO EXTN DEPRESSED, MAIN RELAY (PRESUME THIS IS A) IN PLINTH IS NOT OPERATED. HOWEVER, IT DOES OPERATE WHEN SOMEBODY LIFTS ONE OF THE EXTENSIONS AND PRESSES THE CALL EXCHANGE BUTTON.
YOU MENTION TERMINAL 4 AND 9, IS THAT ELECTRICALLY CONNECTED DUE TO THE SWITCH AS MINE IS NOT HARD WIRED THIS WAY (SEE FURTHER DOWN).

The relay in the ringing converter has one contact. This conects the +v side of the PSU to one side of the buzzer, the other side of the buzzer goes to the -ve side of the PSU via contact A3.

OK. Now I believe you said the extensions do ring in this mode So there must be a path from the B wire to the appropriate line of the extension, the to 'earth' and back to the A wire.

So there seem to be several possibilites :

1) Contact A2 is closed for some reason, shorting out the relay coil

2) The relay in the ringing converter is not operating for some reason.

3) Contact A3 is open for some reason

4) The buzzer is faulty

5) The PSU is defective.

ARE THE CONTACTS A2 & A3 WITHIN ‘MAIN’ RELAY A IN PLINTH? THIS RELAY ACTIVATES WHEN EXCH TO EXTN IS DEPRESSED & MAIN HANDSET IS LIFTED OR AN EXTENSION HANDSET IS LIFTED & CALL EXCHANGE BUTTON IS PRESSED. OTHER THAN WITH MANUAL INTERVENTION I HAVE NOT SEEN RING CONV RELAY OPERATE UNDER ANY CONDITION OF PLANSET OPERATION. BUZZER SOUNDS WHEN RING CONV RELAY PRESSED MANUALLY OR WHEN EXTENSIONS CALL MAIN WITH ALL BUTTONS RELEASED. PSU PRESUMED OK.

Start by taking the cover off the ringing converter. The relay is obvious. Now have an incoming call. Does it operate? If not then either relay A is operated for some reaso or the wiring is wrong.

AS STATED IT DOES NOTHING. RELAY A (AGAIN, ASSUMING THIS IS THE COMPLEX RELAY WITHIN PLINTH) IS NOT OPERATED ON AN INCOMING EXCHANGE CALL.

Maybe the line current sense reed relay LS has stuck closed? That would cause A to be energised.

PLEASE ADVISE WHERE REED RELAY LS CAN BE FOUND. AS STATED RELAY IS ENERGISED WHEN EXTENSION PRESSES CALL EXCHANGE BUTTON BUT DOES NOT APPEAR TO BE ON AN INCOMING CALL.

Using page 3 of N4507 I have tried to trace the ring converter wiring back to terminal block. It seems correct, though it was made more difficult to check as the wires which should have been white/green, white/orange etc were all just plain white!

In my own simple terms, here is how the ring converter relay coil is connected. Perhaps the next step would be if you could see if you agree and then perhaps suggest some further testing?

4 of ring conv goes to 14 on TB which then goes to 1 on plinth using green/brown wire. (This has 2x blue wires feeding off it.)

5 of ring conv goes to 9 on TB which then goes to 9 on plinth (and bridged to 10) using green/red wire. (This has white/brown and white/green wires feeding off it.)

Apologies once again I have had to simplify things and probably not answered all your questions. This is very much a learning curve for me. I much appreciate the time you have all spent with your responses, thank you.

Jason